RE: [PATCH v7 1/6] vfio/type1: Introduce iova list and add iommu aperture validity check

From: Shameerali Kolothum Thodi
Date: Mon Jul 08 2019 - 03:07:24 EST

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Hi Eric,

> -----Original Message-----
> From: Auger Eric [mailto:eric.auger@xxxxxxxxxx]
> Sent: 07 July 2019 16:03
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>;
> alex.williamson@xxxxxxxxxx; pmorel@xxxxxxxxxxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; Linuxarm <linuxarm@xxxxxxxxxx>; John
> Garry <john.garry@xxxxxxxxxx>; xuwei (O) <xuwei5@xxxxxxxxxx>;
> kevin.tian@xxxxxxxxx
> Subject: Re: [PATCH v7 1/6] vfio/type1: Introduce iova list and add iommu
> aperture validity check
>
> Hi Shameer,
>
> On 6/26/19 5:12 PM, Shameer Kolothum wrote:
> > This introduces an iova list that is valid for dma mappings. Make
> > sure the new iommu aperture window doesn't conflict with the current
> > one or with any existing dma mappings during attach.
> >
> > Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
> > ---
> > drivers/vfio/vfio_iommu_type1.c | 181
> +++++++++++++++++++++++++++++++-
> > 1 file changed, 177 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> > index add34adfadc7..970d1ec06aed 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -1,4 +1,3 @@
> > -// SPDX-License-Identifier: GPL-2.0-only
> > /*
> > * VFIO: IOMMU DMA mapping support for Type1 IOMMU
> > *
> > @@ -62,6 +61,7 @@ MODULE_PARM_DESC(dma_entry_limit,
> >
> > struct vfio_iommu {
> > struct list_head domain_list;
> > + struct list_head iova_list;
> > struct vfio_domain *external_domain; /* domain for external user */
> > struct mutex lock;
> > struct rb_root dma_list;
> > @@ -97,6 +97,12 @@ struct vfio_group {
> > bool mdev_group; /* An mdev group */
> > };
> >
> > +struct vfio_iova {
> > + struct list_head list;
> > + dma_addr_t start;
> > + dma_addr_t end;
> > +};
> > +
> > /*
> > * Guest RAM pinning working set or DMA target
> > */
> > @@ -1401,6 +1407,146 @@ static int vfio_mdev_iommu_device(struct
> device *dev, void *data)
> > return 0;
> > }
> >
> > +/*
> > + * This is a helper function to insert an address range to iova list.
> > + * The list starts with a single entry corresponding to the IOMMU
> The list is initially created with a single entry ../..
> > + * domain geometry to which the device group is attached. The list
> > + * aperture gets modified when a new domain is added to the container
> > + * if the new aperture doesn't conflict with the current one or with
> > + * any existing dma mappings. The list is also modified to exclude
> > + * any reserved regions associated with the device group.
> > + */
> > +static int vfio_iommu_iova_insert(struct list_head *head,
> > + dma_addr_t start, dma_addr_t end)
> > +{
> > + struct vfio_iova *region;
> > +
> > + region = kmalloc(sizeof(*region), GFP_KERNEL);
> > + if (!region)
> > + return -ENOMEM;
> > +
> > + INIT_LIST_HEAD(&region->list);
> > + region->start = start;
> > + region->end = end;
> > +
> > + list_add_tail(&region->list, head);
> > + return 0;
> > +}
> > +
> > +/*
> > + * Check the new iommu aperture conflicts with existing aper or with any
> > + * existing dma mappings.
> > + */
> > +static bool vfio_iommu_aper_conflict(struct vfio_iommu *iommu,
> > + dma_addr_t start, dma_addr_t end)
> > +{
> > + struct vfio_iova *first, *last;
> > + struct list_head *iova = &iommu->iova_list;
> > +
> > + if (list_empty(iova))
> > + return false;
> > +
> > + /* Disjoint sets, return conflict */
> > + first = list_first_entry(iova, struct vfio_iova, list);
> > + last = list_last_entry(iova, struct vfio_iova, list);
> > + if (start > last->end || end < first->start)
> > + return true;
> > +
> > + /* Check for any existing dma mappings outside the new start */
> s/outside/below
> > + if (start > first->start) {
> > + if (vfio_find_dma(iommu, first->start, start - first->start))
> > + return true;
> > + }
> > +
> > + /* Check for any existing dma mappings outside the new end */
> s/outside/beyond
> > + if (end < last->end) {
> > + if (vfio_find_dma(iommu, end + 1, last->end - end))
> > + return true;
> > + }
> > +
> > + return false;
> > +}
> > +
> > +/*
> > + * Resize iommu iova aperture window. This is called only if the new
> > + * aperture has no conflict with existing aperture and dma mappings.
> > + */
> > +static int vfio_iommu_aper_resize(struct list_head *iova,
> > + dma_addr_t start, dma_addr_t end)
> > +{
> > + struct vfio_iova *node, *next;
> > +
> > + if (list_empty(iova))
> > + return vfio_iommu_iova_insert(iova, start, end);
> > +
> > + /* Adjust iova list start */
> > + list_for_each_entry_safe(node, next, iova, list) {
> > + if (start < node->start)
> > + break;
> > + if (start >= node->start && start < node->end) {
> > + node->start = start;
> > + break;
> > + }
> > + /* Delete nodes before new start */
> > + list_del(&node->list);
> > + kfree(node);
> > + }
> > +
> > + /* Adjust iova list end */
> > + list_for_each_entry_safe(node, next, iova, list) {
> > + if (end > node->end)
> > + continue;
> > + if (end > node->start && end <= node->end) {
> > + node->end = end;
> > + continue;
> > + }
> > + /* Delete nodes after new end */
> > + list_del(&node->list);
> > + kfree(node);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static void vfio_iommu_iova_free(struct list_head *iova)
> > +{
> > + struct vfio_iova *n, *next;
> > +
> > + list_for_each_entry_safe(n, next, iova, list) {
> > + list_del(&n->list);
> > + kfree(n);
> > + }
> > +}
> > +
> > +static int vfio_iommu_iova_get_copy(struct vfio_iommu *iommu,
> > + struct list_head *iova_copy)
> > +{
> > + struct list_head *iova = &iommu->iova_list;
> > + struct vfio_iova *n;
> > + int ret;
> > +
> > + list_for_each_entry(n, iova, list) {
> > + ret = vfio_iommu_iova_insert(iova_copy, n->start, n->end);
> > + if (ret)
> > + goto out_free;
> > + }
> > +
> > + return 0;
> > +
> > +out_free:
> > + vfio_iommu_iova_free(iova_copy);
> > + return ret;
> > +}
> > +
> > +static void vfio_iommu_iova_insert_copy(struct vfio_iommu *iommu,
> > + struct list_head *iova_copy)
> > +{
> > + struct list_head *iova = &iommu->iova_list;
> > +
> > + vfio_iommu_iova_free(iova);
> > +
> > + list_splice_tail(iova_copy, iova);
> > +}
> > static int vfio_iommu_type1_attach_group(void *iommu_data,
> > struct iommu_group *iommu_group)
> > {
> > @@ -1411,6 +1557,8 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > int ret;
> > bool resv_msi, msi_remap;
> > phys_addr_t resv_msi_base;
> > + struct iommu_domain_geometry geo;
> > + LIST_HEAD(iova_copy);
> >
> > mutex_lock(&iommu->lock);
> >
> > @@ -1487,6 +1635,25 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > if (ret)
> > goto out_domain;
> >
> > + /* Get aperture info */
> > + iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY,
> &geo);
> > +
> > + if (vfio_iommu_aper_conflict(iommu, geo.aperture_start,
> > + geo.aperture_end)) {
> > + ret = -EINVAL;
> > + goto out_detach;
> > + }
> > +
> > + /* Get a copy of the current iova list and work on it */
> At this stage of the reading it is not obvious why you need a copy of
> the list. rationale can be found when reading further or in the series
> history ("Use of iova list copy so that original is not altered in case
> of failure").
>
> Adding a comment in the code would be useful I think.

Ok. That makes sense. I will address this and all other minor comments
you had on other patches in next revision.

Thanks,
Shameer

> Thanks
>
> Eric
>
> > + ret = vfio_iommu_iova_get_copy(iommu, &iova_copy);
> > + if (ret)
> > + goto out_detach;
> > +
> > + ret = vfio_iommu_aper_resize(&iova_copy, geo.aperture_start,
> > + geo.aperture_end);
> > + if (ret)
> > + goto out_detach;
> > +
> > resv_msi = vfio_iommu_has_sw_msi(iommu_group, &resv_msi_base);
> >
> > INIT_LIST_HEAD(&domain->group_list);
> > @@ -1520,8 +1687,7 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > list_add(&group->next, &d->group_list);
> > iommu_domain_free(domain->domain);
> > kfree(domain);
> > - mutex_unlock(&iommu->lock);
> > - return 0;
> > + goto done;
> > }
> >
> > ret = vfio_iommu_attach_group(domain, group);
> > @@ -1544,7 +1710,9 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > }
> >
> > list_add(&domain->next, &iommu->domain_list);
> > -
> > +done:
> > + /* Delete the old one and insert new iova list */
> > + vfio_iommu_iova_insert_copy(iommu, &iova_copy);
> > mutex_unlock(&iommu->lock);
> >
> > return 0;
> > @@ -1553,6 +1721,7 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
> > vfio_iommu_detach_group(domain, group);
> > out_domain:
> > iommu_domain_free(domain->domain);
> > + vfio_iommu_iova_free(&iova_copy);
> > out_free:
> > kfree(domain);
> > kfree(group);
> > @@ -1692,6 +1861,7 @@ static void *vfio_iommu_type1_open(unsigned
> long arg)
> > }
> >
> > INIT_LIST_HEAD(&iommu->domain_list);
> > + INIT_LIST_HEAD(&iommu->iova_list);
> > iommu->dma_list = RB_ROOT;
> > iommu->dma_avail = dma_entry_limit;
> > mutex_init(&iommu->lock);
> > @@ -1735,6 +1905,9 @@ static void vfio_iommu_type1_release(void
> *iommu_data)
> > list_del(&domain->next);
> > kfree(domain);
> > }
> > +
> > + vfio_iommu_iova_free(&iommu->iova_list);
> > +
> > kfree(iommu);
> > }
> >
> >

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